Technical Field
The invention relates to a method for monitoring power supply, in particular to a method for monitoring power supply to the implantable medical device which is implantable in organism.
Related Art
Currently, through the advancement of technology, medical devices, namely implantable medical devices, have already been miniaturized so that they can be implanted inside human bodies for various treatment applications. For example, the implantable medical devices are implantable nerve stimulation devices, glucose sensors or pacemakers, etc. Because the power source is necessary for these devices, micro battery is commonly utilized as the power supply. However, the lifetime of the micro battery is not long enough, so it is not appropriate to the implantable medical device.
Due to battery lifetime, recent development has chosen to transmit power through wireless means. Although wireless power suffers inferior efficiency compared to wired power, it has other advantages of application to the implantable medical devices. In details, if the implantable medical device is equipped with wireless power, the patient may get rid of the risk of battery failure or be relieved from suffering another surgery due to battery exhaustion. Furthermore, wireless power also enhances the operation lifetime of the implantable medical device.
Recently, wireless power technique such as resonant inductive coupling is generally employed in the wireless transmission of electrical power. The transmission end and the reception end all have LC resonance mechanisms so that the transmission end is easier in producing high-power time-varying current, corresponding magnetic fluxes are induced on the inductive coils, and the reception end is easier in obtaining the transmitted energy.
When wireless power technique is applied to the implantable medical device, usually the reception coil has to be aligned with the transmission coil in an external control device so as to obtain the highest amount of energy. If the transmission and reception coils are perpendicular, a less amount of energy is received and the implantable medical device may not be able to function. Thus, the depth or position or other factor of the implantable medical device inside the organism also affects alignment and it may cause poor efficiency of wireless power. Besides, the implantable medical device may obtain different amounts of power due to the distance and alignment between the transmission and reception coils. If the received power is too high, the temperature of the implantable medical device rises and it may even exceed the maximum voltage limitation of the implantable medical device and cause the circuit broken. If the received power is too low, the implantable medical device is not able to operate due to lack of sufficient supplied power.
Therefore, a method for monitoring power supply to the implantable medical device implanted inside the organism particularly inside the patient is expected to monitor the power supply status and timely effectively adjust the transmission power for optimized performance during wirelessly powered by an external control device.